The present invention relates to gradient index optical fibers and, more particularly, to a two-row bundled array of such fibers forming a lens array which transmits an image of an object at an object plane to an image plane at a magnification other than unity.
Image transmitters comprising bundled gradient index optical fibers are known in the art. U.S. Pat. No. 3,658,407 describes a light conducting fiber made of glass or synthetic resin which has a refractive index distribution in a cross-section thereof that varies parabolically outward from a center portion thereof. Each fiber acts as a focusing lens to transmit part of an image of an object placed near one end. An assembly of fibers, in a staggered two-row array, transmits and focuses an image, at 1:1 magnification, of the object. The fiber lenses are produced under the trade name SELFOC; the mark is registered in Japan and owned by Nippon Sheet Glass Co., Ltd.
Numerous techniques are known in the art for manufacturing glass or plastic fibers with index-of-refraction variations. These are usefully summarized in an article entitled "Gradient Index Optics: A Review" by Duncan T. Moore, Applied Optics, 1 Apr. 1980, Volume 19, No. 7, pp. 1035-1038.
It is also known in the art to construct a gradient index lens array capable of forming reduced or enlarged images of a document. Such a lens array is disclosed in U.S. Pat. No. 4,331,380. In this patent, specific designs are provided for a one-row array while variations of a two-row design are more broadly disclosed. It is an object of the present invention to provide an improved embodiment of a two-row design. More specifically, the present invention relates to an optical system for transmitting an image of an object lying in an object plane onto a parallel image plane at a magnification other than unity, said system comprising a gradient index lens array having a plurality of gradient index optical fibers aligned in two rows, the optical centers of each row lying along a symmetrical axis extending along the length direction of the lens array, each fiber in each row having an axis which is substantially nonparallel to the axes of adjoining fibers, the array further characterized by one row having a center fiber through which a plane extended in the width direction forms a right angle with said object and image planes.